Method for adapting an engagement point of a vehicle clutch

ABSTRACT

A method for adapting an engagement point of a disconnect clutch that can be moved between at least one engaged state, in which an output shaft of an internal combustion engine for propelling a vehicle is coupled by way of the disconnect clutch to a rotor of an electric machine for propelling the vehicle, and at least one disengaged state, in which the output shaft is decoupled from the rotor.

The invention relates to a method for adapting an engagement point of adisconnect clutch for a vehicle according to the preamble of patentclaim 1.

Such a method for adapting an engagement point of a disconnect clutchfor a vehicle is known, for example, from DE 102 28 709 A1. Thedisconnect clutch can be moved between at least one closed or engagedstate and at least one opened or disengaged state. In the engaged state,an output shaft of an internal combustion engine for propelling avehicle is coupled via the disconnect clutch to a rotor of an electricmachine for propelling the vehicle. In the disengaged state, the outputshaft is decoupled from the rotor. In other words, the output shaft inthe disengaged state of the disconnect clutch is not coupled via thedisconnect clutch to the rotor.

The engagement point of the disconnect clutch is also called the touchpoint and it is, for example, the position in which the disconnectclutch transmits a predetermined, small torque. In other words, theengagement or touch point is to be understood, for example, as theposition in which the disconnect clutch couples a first shaft, such as,for example, the output shaft, to a second shaft, such as, for example,the rotor, so that, for example, a rotation of the first shaft isinfluenced by the second shaft via the disconnect clutch, for example,to a certain degree, and vice versa. By the adapting of the engagementor touch point, for example, it is possible to compensate forwear-related and/or temperature-caused changes in the engagement point,so that an automatic engaging and disengaging of the disconnect clutch,that is, an engaging and disengaging performed, for example, by means ofan electronic computing device by way of at least one actuator, can beaccomplished as needed, especially in a comfortable manner. By theengaging of the disconnect clutch is meant the moving of the disconnectclutch from the disengaged state to the engaged state. By thedisengaging of the disconnect clutch is meant the moving of thedisconnect clutch from the engaged state to the disengaged state.

Furthermore, WO 2009/127459 A1 discloses a control/regulating device fora vehicle propulsion having at least one drive assembly and oneautomatic clutch situated in a drive train of the vehicle drive unit,which is disengaged or engaged upon passing between two consecutiveidling states. At least one idle regulator with an integrator isprovided for regulating an idling rotational speed of the driveassembly. Moreover, it is provided that a control operation occursduring the transition, in order to avoid deviations between an actualvalue of the idling rotational speed and a desired value.

Furthermore, DE 10 2013 220 399 A1 discloses a method for controlling ahybrid drive train with an internal combustion engine having acrankshaft and an electric machine situated in a belt pulley plane ofthe internal combustion engine and standing in operative connection withthe crankshaft by means of a shiftable planetary gearbox. The planetarygearbox during a starting process of the internal combustion engine iscontrolled by an actuator to move along an actuation path to apredetermined engaging position, activating a brake situated between aring gear of the planetary gearbox and a rotationally fixed housing. Itis provided that the engaging position is compared to a touch pointbetween ring gear and housing, this touch point being determined bymeans of a gradient change ascertained from an electric control variableof the actuator and a travel velocity of the actuator, and is adjustedas a function of this.

The object of the present invention is to further develop a method ofthe kind mentioned above so that the engagement point of the disconnectclutch can be adapted especially precisely and quickly.

This object is achieved according to the invention by a method with thefeatures of patent claim 1. Advantageous embodiments with expedientenhancements of the invention are indicated in the other claims.

The invention relates to a method for adapting an engagement point of adisconnect clutch of a vehicle, especially a motor vehicle such as ahybrid vehicle. The disconnect clutch can be moved between at least oneengaged state and at least one disengaged state. In the engaged state,an output shaft of an internal combustion engine for propelling thevehicle is coupled via the disconnect clutch to a rotor of an electricmachine for propelling the vehicle. In the disengaged state, the outputshaft is decoupled from the rotor. In other words, the output shaft inthe disengaged state of the disconnect clutch is not coupled via thedisconnect clutch to the rotor of the electric machine.

Now, in order to adapt the engagement point of the disconnect clutchespecially precisely and quickly, that is, in a short time, the methodaccording to the invention involves a first step, during which theinitially activated internal combustion engine is deactivated and theinitially engaged disconnect clutch is disengaged. In other words,starting from an operating state in which the internal combustion engineis activated and a disconnect clutch is engaged, the internal combustionengine is deactivated and the disconnect clutch is disengaged. By thedisengaging of the disconnect clutch is meant that the clutch is movedfrom the engaged state to the disengaged state. Accordingly, by anengaging of the disconnect clutch is meant that the clutch is moved fromits disengaged state to its engaged state.

By the deactivating of the internal combustion engine is meant that afired operation of the internal combustion engine is ended, so that theinternal combustion engine is switched from its fired operation to itsunfired or non-fired operation. Accordingly, by the activated internalcombustion engine is meant that the internal combustion engine isoperated in its fired operation. Hence, by an activating of the internalcombustion engine is meant that the unfired or non-fired operation ofthe internal combustion engine is ended, so that the initiallydeactivated internal combustion engine is switched from its unfiredoperation to its fired operation. Accordingly, the deactivated internalcombustion engine is understood to mean that the internal combustionengine is in its unfired or non-fired operation or not in its firedoperation. In the unfired operation of the internal combustion engine,no combustion processes take place in its combustion chambers, which aredesigned, for example, as cylinders.

In a second step of the method according to the invention, while thedisconnect clutch is disengaged and the internal combustion engine isdeactivated, a first course or curve of the rotational speed of theoutput shaft is recorded. The rotational speed of the output shaft or,in particular, the time function of the rotational speed of the outputshaft is recorded, for example, from a first rotational speed to thesecond rotational speed of the output shaft. Since the disconnect clutchis disengaged and the internal combustion engine is deactivated whilethe first curve is being recorded, the rotational speed of the outputshaft or the curve of the rotational speed of the output shaft usuallydecreases from the first rotational speed to the second rotationalspeed.

In a third step of the method, a friction torque of the internalcombustion engine is calculated as a function of at least onepredetermined moment of inertia of the internal combustion engine and afirst rotational speed gradient, which is determined from the recordedfirst curve. For example, the first rotational speed gradient isdetermined from a first rotational speed interval of the first curve.The first rotational speed interval is, for example, at least a firstpart of the first curve. The first rotational speed gradient thusdescribes a change in the rotational speed of the output shaft or thecurve of the rotational speed of the output shaft in the firstrotational speed interval.

The moment of inertia of the internal combustion engine is saved, forexample, in a storage device, especially an electronic computing device.The friction torque of the internal combustion engine is calculated, forexample, by means of the electronic computing device, which is alsodesignated as a controller, in that the electronic computing deviceretrieves the saved moment of inertia from the storage device.Furthermore, the electronic computing device determines, in particularcalculates, as a function of the recorded first curve, the firstrotational speed gradient, so that ultimately the friction torque of theinternal combustion engine is calculated as a function of the firstrotational speed gradient and as a function of the given moment ofinertia. For this, the first rotational speed gradient is multiplied bythe given moment of inertia.

In a fourth step of the method, preferably coming after the first stepand the second step, the disconnect clutch is moved in the direction ofits engaged state. This should be taken to mean, for example, that thedisconnect clutch, starting from its disengaged state, is moved from thedisengaged state in the direction of the engaged state, but not entirelyinto the engaged state, so that the disconnect clutch takes up anintermediate state, for example, one lying between the engaged state andthe disengaged state.

In a fifth step of the method, while the disconnect clutch is beingmoved in the direction of its engaged state and the internal combustionengine is still deactivated, a second curve of the rotational speed ofthe output shaft is recorded, coming after the first curve. In a sixthstep of the method, a second rotational speed gradient is determinedfrom the recorded second curve. For example, the second rotational speedgradient is determined from a second rotational speed interval of thesecond curve, wherein the second rotational speed interval is at least asecond part of the second curve, for example. The second rotationalspeed interval, for example, comes later in time than the firstrotational speed interval and extends, for example, from a thirdrotational speed, which is different from the first and the secondrotational speed, to a fourth rotational speed, which is different fromthe first, the second, and the third rotational speeds, so that thesecond curve describes the rotational speed and especially the change inthe rotational speed of the output shaft in the second rotational speedcurve.

For example, the disconnect clutch in the second rotational speedinterval is moved in the direction of its engaged state or is alreadyfound in the intermediate state. Since the disconnect clutch isdisengaged when recording the first curve, the first curve or therotational speed of the output shaft is not influenced by the electricmachine when recording the first curve. Since, during the recording ofthe second curve, the disconnect clutch is moved from its disengagedstate in the direction of its engaged state, there occurs an influencingof the rotational speed of the output shaft, brought about by theelectric machine, for example, during the recording of the second curve,and this influencing is recognizable with the help of the second curve.

In a seventh step of the method, a reaction moment of the disconnectclutch, especially a reaction moment of the disconnect clutch resultingfrom the moving of the disconnect clutch from its disengaged state inthe direction of its engaged state, is determined as a function of thecalculated friction torque, the second rotational speed gradient, andthe predetermined moment of inertia of the internal combustion engine.For example, the second rotational speed gradient is multiplied by themoment of inertia of the internal combustion engine. This multiplicationresults, for example, in an overall torque, from which the previouslycalculated friction torque is subtracted. The result of this subtractionis, for example, the mentioned reaction moment. Finally, in an eighthstep of the method, the engagement point of the disconnect clutch isadapted as a function of the determined reaction moment.

In the course of the fourth step, that is, when moving the disconnectclutch in the direction of its engaged state, the disconnect clutch isactuated by the electronic computing device, for example on the basis ofa characteristic curve. This actuation results in the reaction momentand hence the described influencing of the rotational speed, especiallyits second curve. In the context of the method, therefore, the reactionmoment resulting from the actuating of the disconnect clutch isdetermined. If the reaction moment corresponds to a desired moment, forexample, the actuation and thus the engagement point, also known as thetouch point, need not be changed.

However, if the determined reaction moment deviates, for example, fromthe desired moment, the actuation and hence the engagement point may bechanged such that the deviation of the determined reaction moment fromthe desired moment is decreased or even abolished. Thus, the engagementor touch point can be adapted especially precisely and quickly, that is,in only a short time, by means of the method of the invention, sinceonly the recorded curves of the rotational speed of the output shaft andthe predetermined and, in particular, memorized friction torque of theinternal combustion engine need to be consulted.

In particular, the invention is based on the understanding thatsituations, especially driving situations, often occur during a normaloperation of the vehicle, in which the method can be carried out withoutnoticeably influencing the respective driving situation for thepassengers of the vehicle. Hence, it is possible with the method of theinvention to adapt the engagement point sufficiently often and preciselyduring the operation of the vehicle. Such driving situations in which itis especially advantageous to carry out the method of the inventionoccur, in particular, when a hybrid flow control demands a transitionfrom a hybrid driving to an electric driving. By hybrid driving is meanta mode or a driving state of the vehicle in which the vehicle is drivenboth by means of the electric machine and also by means of the internalcombustion engine. By electric driving is meant a mode or a drivingstate of the vehicle in which the vehicle is driven solely by means ofthe electric machine, but not by means of the internal combustionengine.

In the course of the electric driving, the internal combustion enginemay thus be shut off, that is, separated from the electric machine anddeactivated. For the separating of the internal combustion engine fromthe electric machine, the disconnect clutch is disengaged, whereby theoutput shaft or the internal combustion engine is separated from theelectric machine or the rotor of the electric machine. The method of theinvention utilizes a transition from hybrid driving to electric drivingwherein, during this transition, the output shaft coasts or ceasesrotating, so that its rotational speed successively approaches 0. Thisrotational speed decrease or rotational speed change is utilized in thescope of the method of the invention to adapt the engagement point ofthe disconnect clutch in the described manner.

Hence, the method is further based on the understanding that therotational speed gradient of the internal combustion engine or theoutput shaft is determined by only two quantities or values during thetransition, that is, in a phase where the disconnect clutch isdisengaged and the internal combustion engine is deactivated: a firstquantity is the moment of inertia of the internal combustion engine, themoment of inertia also being known as the inertia factor. The secondquantity is the friction torque of the internal combustion engine. Bothquantities are known or can be ascertained in the manner described. Inthe third step, the friction torque of the internal combustion engine isverified, in order to finally calculate precisely the reaction moment ofthe disconnect clutch, so that the engagement point can be preciselyadapted as a consequence.

By moving the disconnect clutch from the disengaged state in thedirection of the engaged state, the rotational speed gradient in thesecond curve is influenced or changed as compared to the first curve, sothat this rotational speed gradient change can be used to calculate aperturbing moment produced by the disconnect clutch and consequently,the reaction moment of the disconnect clutch.

In an advantageous embodiment of the invention, it is provided that noactivating of the internal combustion engine occurs at least between thefirst step and the fifth step. This avoids any influencing of therotational speed gradient caused by an activating of the internalcombustion engine, so that the respective rotational speed gradient andhence the reaction moment can be ascertained especially precisely. Afterthis, the engagement point can be precisely adapted. Moreover, thisembodiment is based on the idea of ascertaining the curves of therotational speed, and thus the rotational speed gradient, withinprecisely one transition from hybrid to electric driving, withoutactivating the internal combustion engine, so that the engagement pointcan be adapted especially quickly and precisely.

It is possible to break off or interrupt the adaptation and to activatethe internal combustion engine for this purpose after the first stepand, for example, before at least one of the remaining steps of themethod. Such an activating of the internal combustion engine is alsocalled a switching on of the internal combustion engine. A demand toswitch on the internal combustion engine will arrive, for example, basedon a desire of the driver to have traction power, which can be providedby activating the internal combustion engine. Such a desire for tractionpower takes precedence over the adapting of the engagement point, sothat the adapting is broken off or interrupted in order to switch on theinternal combustion engine and satisfy the desire for traction power.Because situations in which the method can be carried out and thus theengagement point can be adapted may occur often in a normal operation,the described interrupting or terminating of the adaptation does notinvolve a disadvantage.

In this regard, moreover, it has been shown to be advantageous for therotational speed of the output shaft to always be greater than 0, atleast between the first step and the fifth step. In other words, thecurves and the rotational speed gradient resulting from the disengagingof the disconnect clutch are determined before the output shaft comes toa standstill. Moreover, it has been shown to be an advantage when thereis no engaging of the disconnect clutch or no moving of the disconnectclutch in the direction of its engaged state, at least between the firststep and the fourth step.

In an advantageous embodiment of the invention, the rotational speedgradient is determined from the aforementioned rotational speedintervals of the respective curves, wherein the rotational speed of theoutput shaft in the respective rotational speed intervals is alwaysgreater than 0. Thus, no standstill of the output shaft occurs either inor between the rotational speed intervals, so that the engagement pointcan be adapted especially quickly.

In an especially advantageous embodiment of the invention it is providedthat at least the first step, the second step, the fourth step and thefifth step are carried out while the vehicle is moving and rolling byits wheels along a roadway. In this way, the engagement point can beadapted precisely and sufficiently often during a normal drivingoperation of the vehicle, so that, for example, thermally related and/orwear-related changes in the engagement point can be compensatedespecially advantageously. Moreover, it has been shown to beadvantageous when no standstill of the vehicle occurs, at least betweenthe first step and the fifth step.

Another embodiment is characterized in that at least the first step, thesecond step, the fourth step and the fifth step are carried out whilethe vehicle is being driven by means of the electric machine. In thisway, the engagement point can be adapted during a normal operation ofthe vehicle, without making this operation noticeable to the passengersof the vehicle.

Finally, it has been shown to be especially advantageous for thedisconnect clutch, during the fifth step, to be moved in the directionof its engaged state in such a way that the reaction moment lies in arange of 10 Newton-meters up to and including 20 Newton-meters. In thisway, an especially precisely recordable influencing or changing of therotational speed gradient can be accomplished, so that the reactionmoment can be precisely ascertained with the aid of the especiallyprecisely recorded change in the rotational speed gradient. As a result,the engagement point can be adapted especially precisely.

The invention also includes a method for operating a motor vehicle,especially a hybrid vehicle, by means of a method according to theinvention. In other words, it is preferably proposed to employ themethod of the invention in a motor vehicle, especially in a hybridvehicle, whereby an especially advantageous operation as well as a morecomfortable and efficient operation of the motor vehicle can be realizedby means of the method according to the invention.

Further advantages, features and details of the invention will emergefrom the following description of a preferred exemplary embodiment aswell as the drawing. The features and combinations of features mentionedabove in the description, as well as the features and combinations offeatures mentioned in the description of the figures, and/or depictedstanding alone in the figures, may be used not only in the particularindicated combination, but also in other combinations or standing alone,without leaving the scope of the invention.

The drawing shows in:

FIG. 1 a schematic representation of a drive train for a vehicle,wherein a method is carried out by means of which an engagement point ofa disconnect clutch of the drive train can be adapted especiallyprecisely and quickly; and

FIG. 2 a diagram to illustrate the method.

In the figures, the same or functionally identical elements are giventhe same reference numbers.

FIG. 1 shows, in a schematic representation, a drive train for avehicle, denoted as overall by reference 10, the vehicle being designedas a motor vehicle, especially a hybrid vehicle. The drive train 10comprises an internal combustion engine 12, which is designed as areciprocating internal combustion machine. The internal combustionengine 12 comprises a cylinder housing 14, in which a plurality ofcombustion chambers are formed in the shape of cylinders 16. Moreover,the internal combustion engine 12 comprises an output shaft, designed asa crankshaft 18, which is mounted, for example, on a housing element ofthe internal combustion engine 12 and can rotate about a rotary axisrelative to the housing element. By way of the crankshaft 18, theinternal combustion engine 12 provides torques for driving the motorvehicle. The motor vehicle furthermore comprises wheels, by which themotor vehicle can roll along a roadway during driving, especially duringforward driving. Of these wheels, two wheels of the motor vehicle areshown in FIG. 1, denoted as reference 20. The wheels 20 are so-calleddriven or drivable wheels, since the wheels 20 can be driven by means ofthe internal combustion engine 12 via the crankshaft 18. The drive train10 is designed as an alternative drive and comprises an electric machine22. The wheels 20 and the motor vehicle overall can be propelled bymeans of the internal combustion engine 12 and also by means of theelectric machine 22. The internal combustion engine 12 comprises, forexample, a stator 24 shown very schematically in FIG. 1. Moreover, theelectric machine 22 comprises a rotor 26, which can rotate about an axisof rotation relative to the stator 24. The electric machine 22 can beoperated, for example, in a motor mode and hence as an electric motor.In the motor mode, the rotor 26 is driven by the stator 24. For thispurpose, the electric machine 22 in its motor mode is supplied withelectrical energy or electric current. This electrical energy isprovided for example from an electrical energy accumulator in the formof a battery and supplied to the electric machine 22.

In the present instance, the rotor 26, which comprises, for example, atleast one rotor shaft, is arranged coaxially to the crankshaft 18, sothat the axis of rotation about which the rotor 26 can rotate relativeto the stator 24 coincides with the axis of rotation about which thecrankshaft 18 can rotate relative to the housing element.

The drive train 10 comprises a differential 28. The electric machine 22in its motor mode can provide torques via the rotor 26 for propellingthe wheels 20 and thus for propelling the motor vehicle overall. Thetorques provided by the internal combustion engine 12 via the crankshaft18 as well as the torques provided by the electric machine 22 via therotor 26 for propelling the motor vehicle may be transmitted across thedifferential 28 to the wheels 20, so that the wheels 20 and hence themotor vehicle as a whole are driven.

The drive train 10 further comprises a disconnect clutch 30, which isarranged between the crankshaft 18 and the rotor 26, for example, whenreferred to a flow of torque from the crankshaft 18 to the rotor 26, orvice versa. For example, the disconnect clutch 30 is designed as afriction clutch. In particular, the disconnect clutch 30 is designed asa multi-plate clutch, especially as a wet multi-plate clutch, so thatthe disconnect clutch 30 comprises coupling plates, for example, whichrun in a liquid lubricant, especially oil.

The disconnect clutch 30 can be moved between at least one engaged stateand at least one disengaged state. In particular, the disconnect clutch30 can be moved automatically between the disengaged state and theengaged state. For this purpose, an electronic computing device 32 isprovided, which is also called a controller. The controller actuates thedisconnect clutch 30, so that, for example, the disconnect clutch 30 ismoved by means of the controller automatically between the engaged stateand the disengaged state via an actuator, not shown in detail in FIG. 1.In other words, a movement of the disconnect clutch 30 occurs from thedisengaged state to the engaged state, or vice versa, from acorresponding actuation of the disconnect clutch 30, brought about bythe controller.

In the engaged state, the crankshaft 18 is connected via the disconnectclutch 30 to the rotor 26, so that, for example, torques can betransmitted between the crankshaft 18 and the rotor 26 by way of thedisconnect clutch 30. In the disengaged state, the crankshaft 18 isdecoupled from the rotor 26, so that in the disengaged state, thedisconnect clutch 30 cannot transmit any torques between the crankshaft18 and the rotor 26 by way of the disconnect clutch 30.

In the context of a hybrid driving of the motor vehicle, the disconnectclutch 30 is engaged. In other words, in the course of the hybriddriving, the disconnect clutch 30 is in its engaged state, so that thewheels 20 or the motor vehicle are driven both by means of the electricmachine 22 and also by means of the internal combustion engine 12.

In the context of an electric driving of the motor vehicle, thedisconnect clutch 30 is disengaged, so that the wheels 20 and hence, inregard to the internal combustion engine 12 and the electric machine 22,the motor vehicle are driven only by means of the electric machine 22.Hence, upon transition from hybrid driving to electric driving thereoccurs a disengaging of the disconnect clutch 30. In the course of thisdisengaging, the disconnect clutch 30 is moved or transferred from itsengaged state to its disengaged state. Hence, the disengaged disconnectclutch 30 is understood to mean that the disconnect clutch 30 is in itsdisengaged state.

The disconnect clutch 30 has an engagement point, which is also calledthe touch point. The engagement point is, for example, a position of thedisconnect clutch 30, especially a position of coupling members 34 and36 of the disconnect clutch 30, whereby, for example, a rotation of thecrankshaft 18 by the rotor 26 is influenced via the disconnect clutch 30in this position. In other words, if the disconnect clutch 30 or thecoupling members 34 and 36, for example, are moved from the disengagedstate in the direction of the engaged state, then the engagement pointis that position of the disconnect clutch 30 or the coupling members 34and 36 in which there occurs a transmittal of a given torque by way ofthe disconnect clutch 30 and thus an influencing of the rotation of thecrankshaft 18 by the rotor 26 by way of the disconnect clutch 30, orvice versa. Before reaching this position, no torque or only anegligibly small torque is transmitted by the disconnect clutch 30, orbefore reaching the mentioned position, there is no noticeableinfluencing of the rotation of the crankshaft 18 by the rotor 26 by wayof the disconnect clutch 30, or vice versa.

The engagement point of the disconnect clutch 30 may vary, for example,due to wear and/or temperature. Moreover, it is possible for theengagement point to vary as a result of component tolerances. Such avariation or changing of the engagement point should be compensated inthe course of an adapting of the engagement point, in order to assure anefficient and comfortable operation of the drive train 10 throughout thelong service life of the drive train 10. Namely, by adapting theengagement point, it is possible to adjust the disconnect clutch 30 asneeded and, in particular, comfortably, even with variation of theengagement point, so that, for example, jerky movements of thedisconnect clutch 30, which can be felt by passengers of the motorvehicle, can be avoided. In particular, it is possible by the adaptingof the engagement point to allow large scatter in components in a massproduction process, so that the vehicle can be manufactured easily andeconomically.

Now, in order to adapt the engagement point of the disconnect clutch 30in an especially precise and rapid manner, that is, in a brief time, theinitially activated internal combustion engine 12—especially startingfrom hybrid driving—is deactivated, and the initially engaged disconnectclutch 30 is disengaged.

FIG. 2 shows a diagram for illustrating a method for adapting theengagement point. On the abscissa 38 of the diagram is plotted the timet, and on the ordinate 40 of the diagram is plotted the rotational speedn of the crankshaft 18 and thus of the internal combustion engine 12.For example, at a first time t1, the initially engaged disconnect clutch30 is disengaged and the initially activated internal combustion engine12 is deactivated. On account of the disengaging of the disconnectclutch 30 and on account of the deactivating of the internal combustionengine 12, the rotational speed of the crankshaft 18 decreases, startingfrom the first time t1.

In order to drive the motor vehicle by means of the internal combustionengine 12, the internal combustion engine 12 is operated in its firedoperation. In the course of the fired operation, combustion processestake place in the cylinders 16, during which a particular fuel/airmixture is burned in the respective cylinder 16. By the deactivation ofthe internal combustion engine 12, the fired operation is ended, so thatthe internal combustion engine 12 is transferred from its firedoperation to its unfired operation. The unfired operation is also calledthe non-fired operation, during which no combustion processes take placein the cylinders 16. Hence, starting from the first time t1, thecrankshaft 18 is driven neither by combustion processes taking place inthe cylinders 16 nor by the rotor 26 by way of the disconnect clutch 30,so that the rotational speed of the crankshaft 18 decreases.

During a second step of the method—while the disconnect clutch 30 isdisengaged and the internal combustion engine 12 is deactivated—a firstcurve 42 of the rotational speed of the crankshaft 18 is recorded. Thefirst curve 42 has a first rotational speed interval, which extends froma first rotational speed n1 to a second rotational speed n2 of thecrankshaft 18. Since the rotational speed of the crankshaft 18 isdecreasing starting from the time t1, the second rotational speed n2 isless than the first rotational speed n1. Thus, in the first rotationalspeed interval there occurs a decreasing of the rotational speed of thecrankshaft 18. This decreasing of the rotational speed in the firstrotational speed interval occurs with a first rotational speed gradient,which is determined from the recorded first curve 42, especially beingcalculated by means of the controller.

In a third step of the method, a friction torque of the internalcombustion engine 12 is ascertained as a function of at least one givenmoment of inertia of the internal combustion engine 12 and as a functionof the first rotational speed gradient. The friction torque of theinternal combustion engine 12 is denoted for example as J_(VM) and isstored, for example, in a storage device of the electronic computingdevice 32 (controller). The friction torque of the internal combustionengine 12 is denoted for example as M_(reib). Thus, the friction torqueM_(reib) is given as:

M _(reib) =J _(VM)*{dot over (ω)}_(VM1.)

Here, {dot over (ω)}_(VM1) denotes the mentioned first rotational speedgradient. On the whole, it can be seen from FIG. 2 that there is noinfluencing of the rotational speed of the crankshaft 18 brought aboutby the disconnect clutch 30 in the first rotational speed interval,since the disconnect clutch 30 is and remains disengaged in the firstrotational speed interval.

In the fourth step of the method, the disconnect clutch 30 is moved fromits disengaged state in the direction of its engaged state. For example,at a second time t2, following the first time t1, the moving of thedisconnect clutch 30 in the direction of its engaged state has begun. Bythe moving of the disconnect clutch 30 in the direction of its engagedstate is understood to mean, for example, that the disconnect clutch 30,especially the coupling members 34 and 36, starting from the disengagedstate, are moved or adjusted in the direction of the aforementionedposition, and hence in the direction of the engaged state, but notentirely to the engaged state, for example.

Between the second time t2 and a third time t3, following the secondtime t2, the disconnect clutch 30, despite the commencement of themoving of the disconnect clutch 30 in the direction of the engagedstate, for example, is still disengaged so much that there is noinfluencing of the rotational speed of the crankshaft 18. But startingfrom the third time t3, the rotational speed of the crankshaft 18 andespecially its rotational speed change are influenced by the disconnectclutch 30, since the disconnect clutch 30, especially the couplingmembers 34 and 36, have reached the mentioned engagement point at thethird time t3. In a fifth step of the method—while the disconnect clutch30 is moving in the direction of its engaged state and the internalcombustion engine 12 is still deactivated—a second curve 44 of therotational speed of the crankshaft 18 is recorded. The second curve 44comprises a second rotational speed interval, which extends from a thirdrotational speed n3 to a fourth rotational speed n4, the thirdrotational speed n3 being, for example, less than the second rotationalspeed n2, and the fourth rotational speed n4 being, for example, lessthan the third rotational speed n3. The curves 42 and 44 may be spacedapart from each other. Alternatively, it is conceivable for the secondcurve 44 to border directly on the first curve 42, so that the secondrotational speed n2 corresponds to the third rotational speed n3. In asixth step of the method, a second rotational speed gradient isascertained from the recorded second curve 44. This second rotationalspeed gradient is denoted by {dot over (ω)}_(VM2) and is influenced bythe disconnect clutch 30, since the disconnect clutch 30 has alreadybecome so much engaged, at least during a portion of the second curve 44or the second rotational speed interval, that the rotational speed ofthe crankshaft 18 is influenced by the rotor 26 by way of the disconnectclutch 30.

In a seventh step of the method, a reaction moment M_(K0) of thedisconnect clutch 30 is calculated as a function of the calculatedfriction torque M_(reib), as a function of the second rotational speedgradient {dot over (ω)}_(VM2) and as a function of the given moment ofinertia J_(VM). The reaction moment M_(K0) for example is given as:

M _(K0) =M _(ges) −M _(reib).

Here M_(ges) denotes an overall moment, which is given by:

M _(ges) =J _(VM)*{dot over (ω)}_(VM2).

Since the moment of inertia J_(VM) is given or saved in memory and therotational speed gradients {dot over (ω)}_(VM1) and {dot over (ω)}_(VM2)are determined from the recorded curves 42 and 44, the reaction momentM_(K0) can be calculated quickly and precisely. In this way, during aneighth step of the method, the engagement point can be adapted as afunction of the ascertained reaction moment M_(K0).

In the course of the fourth step of the method, the disconnect clutch 30is moved by a corresponding actuation in the direction of the engagedstate, this actuation occurring from the electronic computing device 32to the disconnect clutch 30. Thus, with the aid of the method, thereaction moment resulting from the corresponding actuation of thedisconnect clutch 30 can be ascertained. For example, if the ascertainedreaction moment corresponds to a desired moment, the actuation need notbe changed. But if the ascertained reaction moment deviates from thedesired moment, this indicates a wear and/or temperature-related changein the engagement point, so that the actuation and hence the engagementpoint may be adapted such that the deviation between the desired momentand the ascertained reaction moment is at least decreased or evenabolished.

The described method may be carried out, in particular, while the motorvehicle is rolling by its wheels 20 along the roadway, and especiallywhile the wheels 20 and the motor vehicle are being driven by means ofthe electric machine 22. In such a normal operation, driving situationsoften occur in which the described method can be carried out, so thatthe engagement point can be adapted sufficiently often and precisely.

1-8. (canceled)
 9. A method for adapting an engagement point of adisconnect clutch that can be moved between at least one engaged state,in which an output shaft of an internal combustion engine for propellinga vehicle is coupled by way of the disconnect clutch to a rotor of anelectric machine for propelling the vehicle, and at least one disengagedstate, in which the output shaft is decoupled from the rotor,comprising: a) deactivating the initially activated internal combustionengine and disengaging the initially engaged disconnect clutch; b) whilethe disconnect clutch is disengaged and the internal combustion engineis deactivated: recording a first curve of the rotational speed of theoutput shaft; c) calculating a friction torque of the internalcombustion engine as a function of at least one predetermined moment ofinertia of the internal combustion engine and a first rotational speedgradient, which is determined from the recorded first curve; d) movingthe disconnect clutch in the direction of its engaged state; e) whilethe disconnect clutch is being moved in the direction of its engagedstate and the internal combustion engine is still deactivated: recordingof a second curve of the rotational speed of the output shaft comingafter the first curve; f) determining a second rotational speed gradientfrom the recorded second curve; g) determining a reaction moment of thedisconnect clutch as a function of the calculated friction torque, thesecond rotational speed gradient and the predetermined moment of inertiaof the internal combustion engine; and h) adapting the engagement pointas a function of the determined reaction moment.
 10. The method asclaimed in claim 9, wherein activation of the internal combustion enginedoes not occur, at least between step a) and step e).
 11. The method asclaimed in claim 9, wherein the rotational speed of the output shaft isalways greater than 0, at least between step a) and step e).
 12. Themethod as claimed in claim 9, wherein the rotational speed gradients aredetermined from respective rotational speed intervals of the respectivecurves, wherein the rotational speed of the output shaft in therespective rotational speed intervals is always greater than
 0. 13. Themethod as claimed in claim 9, wherein at least the steps a), b), d) ande) are carried out while the vehicle is moving and rolling by its wheelson a roadway.
 14. The method as claimed in claim 13, wherein at leastthe steps a), b), d) and e) are carried out while the vehicle is beingdriven by means of the electric machine.
 15. The method as claimed inclaim 9, wherein during step e) the disconnect clutch is moved in thedirection of its engaged state such that the reaction moment lies in arange of 10 Newton-meters up to and including 20 Newton-meters.